di·gress 
(dī-grĕs, dĭ-)
(dī-grĕs, dĭ-)intr.v. di·gressed, di·gress·ing, di·gress·es
To stray temporarily from the topic at hand, as in delivering a speech or engaging in a discussion. See Synonyms at swerve.
[Latin dīgredī, dīgress- : dī-, dis-, apart; see DIS- + gradī, to go; see ghredh- in the Appendix of Indo-European roots.]